Robert Scoble, of all people, was the first to break the news earlier today that Apple had acquired Siri, a company known for their voice-activated personal assistant app for the iPhone and iPod Touch. Notably, the app was selected as the Most Innovated Web Technology at this year’s SXSW conference.

Some are touting Apple’s recent purchase as yet another strike against Google in the growing rivalry between the two companies, with the gist being that integrated Siri-like functionality will let users query information without having to interact with search engines like Google.

But how does Siri work, exactly? Below, check out a demo of app in action.

A Siri user can simply say, “Tell my wife I’ll be 20 minutes late,” and Siri scours the user’s social networks, address books and other programs, finds the person tagged “wife,” converts the message to text, and sends it directly to her phone

While precise terms of the deal remain murky, Siri board member Shawn Carolan told the WSJ that “the offer from Apple was of a scope and tenor that it was a no-brainer to accept it.”

Siri’s voice recognition technology is powered by Nuance Communications’ speech processing engine and TechCrunch’s initial review of the app from February sheds a bit more light on the underlying technology behind Siri.

Siri combines an impressive array of technologies and brings them together on the iPhone. These include natural language processing and semantic analysis. The underlying technology was developed at SRI with $200 million worth of Darpa grants. Siri was spun off to commercialize it and bring it to consumers. It’s last funding round was led by Hong Kong billionaire Li Ka-shing (a fact never disclosed before), who also is an investor in Facebook.

In a way, Siri is the “mother of all mashups.” The iPhone app is a conversational interface with Siri’s servers on the Web, which tie into nearly 30 different APIs at launch, with more on the way. These include OpenTable, TaxiMagic, MovieTikets.com, Rotten Tomatoes, WeatherBug, Yahoo Local, Yahoo Boss, StubHub, Bing, Eventful Freebase, Citysearch, AllMenus.com, Gayot, and Wolfram Alpha.